Method for preventing slumping of a settled bed in inclined pipes

ABSTRACT

Method for preventing downhill slumping in a shutdown slurry pipeline. A helical rib or spiral fin is positioned in the pipeline in those sections of the line where inclination exceeds some predetermined critical angle to prevent the formation of a line plug by the solid phase of the slurry material sliding or slumping toward locations in the pipeline that are susceptible to plugging.

United States Patent Inventor Frank L. Meyer Houston, Tex.

App]. No. 828,266

Filed May 27, 1969 Patented Oct. 5, 1971 Assignee Shell Oil Company NewYork, N.Y.

METHOD FOR PREVENTING SLUMPING OF A SETTLED BED IN INCLINED PIPES 1Claim, 4 Drawing Figs.

U.S. Cl 302/66, 302/14 Int. Cl B65g 53/04 Field of Search 302/14, 64, 66

[56] References Cited UNITED STATES PATENTS 630,605 8/1899 Gordon et al302/64 1,603,653 10/1926 Ward 302/14 3,313,577 4/1967 Wolfe 302/64Primary Examiner-Andres H. Nielsen Attorneys-Thomas R. Lampe and .l. H.McCarthy ABSTRACT: Method for preventing downhill slumping in a shutdownslurry pipeline. A helical rib or spiral fin is positioned in thepipeline in those sections of the line where inclination exceeds somepredetermined critical angle to prevent the formation of a line plug bythe solid phase of the slurry material sliding or slumping towardlocations in the pipeline that are susceptible to plugging.

PATENTEDUET 519m 3610.706

INVENTOR: 4 F. L. MEYER HIS ATTORNEY 1 METHOD FOR PREVENTING SLUMPING OFA SE'ITLED BED IN INCLINED PIPES The present invention relates topipeline transport operations; and more particularly, to a method forpreventing the downward movement of slurry solids in an inclined portionof pipeline during a shutdown period.

Transportation by pipeline is a major and growing industry. With the usethereof formerly confined almost entirely to movement of water, gas andpetroleum products, pipelines, with the advent of slurry transport, havebecome useful for long and short hauls of a wide variety of rawmaterials and finished products.

With respect to the pipeline transportation of materials in slurry form,problems arise when such materials are moved through pipelines inclinedto go over a hill or down into a valley. At these locations, during aplanned or emergency line shutdown, the solids of the transported slurrymay settle out vertically and subsequently slide down the inclinedportions of the pipeline, thereby causing a compacted plug which may bevery difficult to dislodge and move when line shutdown is terminated andtransport activities are attempted.

. These difficulties are most commonly avoided by laying solids-carryingor slurry pipelines so that they do not exceed a slope or angle ofinclination below which sliding does not occur. Alternatively, theinclined pipeline sections are emptied or flushed at each shutdown.Obviously, these alternative prior art approaches are not alwaysfeasible or economical, especially in those situations where long andrelatively steep slopes are encountered. Slopes of this nature are beingencountered with increasing frequency as pipeline operations are beingextended to new relatively inaccessible mountainous areas in the UnitedStates and elsewhere.

SUMMARY OF THE INVENTION It is therefore a primary object of the presentinvention to provide an improved and economical method whereby slurrymaterial being transported in an inclined pipeline section is preventedfrom slumping during a line shutdown.

This and other objects have been attained in the present invention byproviding a method for preventing downhill slumping in a shutdown slurrypipeline wherein a helical or spiral fin is installed in the pipeline inthe sections thereof where the inclination exceeds some critical anglebelow which slumping does not occur. The rib or fin, which may protrudeinto the pipeline interior 0.02 to 0.4 diameters, for example, preventsthe settled bed of the slurry solid phase from sliding down the inclinedportion of the pipeline to form a plug.

DESCRIPTION OF THE DRAWING The above-noted and other objects of thepresent invention will be understood from the following description,taken with reference to the accompanying drawing. In describing theinvention in detail, reference will be made to the drawing in which likereference numerals designate corresponding parts throughout severalviews in which:

FIG. I is a diagrammatic view illustrating a given length of slurrypipeline which has been modified in accordance with the teachings of thepresent invention;

FIG. 2 is an enlarged cross-sectional view in longitudinal projectionillustrating an inclined portion of the pipeline section of FIG. 1 withone form ofspiral fin installed therein;

FIG. 3 is a view similar to that of FIG.. 2 but illustrating analternative formof spiral fin or rib which may be utilized in carryingout the teachings of the present invention;

FIG. 4 'is an enlarged cross-sectional plan'view illustrating a portionof pipeline section incorporating still another alternative form of ribconstruction.

Referring now to FIG. 1, a given length of slurry pipeline 11 isillustrated in the position assumed thereby as the pipeline proceeds-to' and from a valley formed between two hills or mountains l2 and 13.The terrain illustrated is typical of that encountered in pipelinelaying activities, although it should be understood that the teachingsof the present invention may be carried out in any topographicalconfiguration wherein a por tion of slurry pipeline is inclined with thehorizontal.

The transportation of slurries consisting of solid particles in a fluidmedium by use of pipelines similar to that disclosed in FIG. 1 is quitewell known, and such expedient is finding increasing use, especially inthose situations where the source of raw materials is relatively remoteand inaccessible from the point of delivery, which may be a suitableprocessing plant; for example. In the disclosed arrangement, it may beassumed for purposes of illustration that the slurry material beingtransferred through pipeline 11 as by means of pumps (not shown) or bygravitation is moving through the line in the direction indicated by thearrows. However, the teachings of the present invention are, of course,applicable regardless of the direction of flow of the slurry. Thepipeline may, of course, have only one inclination and thereby notcontain a valley.

As long as flow continues in the pipeline, the solid matter of theslurry will remain suspended in the liquid, even when the solid matterhas a higher specific gravity than the liquid. If, however, the flow isstopped for any reason, i.e., the pipeline is shut down or fails, suchsolid particulate matter will settle out of suspension. In the situationwhere the line is horizontal or the slope of the line is insufficient tocause sliding of the settled solids, no problem is created by suchsettling out. Under these conditions, a liquid-rich channel remains openat the top of the line which allows the settled material to beresuspended with a minimum of difficultyupon resumption of flow.

A serious problem can exist when the pipeline must be inclined to goover a hill or down a valley, as illustrated, for example, in FIG. 1. Atthese locations, the settling of solids followed by their sliding downthe slope during a protracted shutdown can result in a compacted plug ofmaterial difficult, if not impractical, to disperse or resuspend. In theillustrated pipeline configuration, such solids would slide downwardlyinto the valley formed between hills or mountains l2 and 13 or to thelower end of a singularly inclined pipe. The solid material would thencompress under its own weight to form a plug in the valley or lower endin an obvious manner.

Such plug formation is prevented in accordance with the teachings of thepresent invention as follows.

Installed within pipeline 11 at preselected locations are helical ribsor spiral tins 21 and 22. FIG. 2 illustrates the construction of one ofthese ,fins or ribs 2] in greater detail and reference may be hadto thatfigure as well as FIG. I for a proper understanding of the operationofone form of tin or rib which may be utilized in carrying out theteachings of the present invention. Rib 21 is in the form of acontinuous helix extending along the inner peripheral wall of pipelineII in abutting engagement therewith. The rib 21 extends or protrudesinto the throughbore defined by pipeline 11 a predetermined distancewhich may be in the order of 0.02 to 0.4 pipeline diameters, forexample. The rib may be secured to the pipeline 11 in any known manner,such as spot welding. Altemately, the rib 21 may be formed integrallywith the pipeline as by means of extrusion or by forming a flange alongone edge of the metal sheet used in constructing the pipeline andhelically winding the sheet around a. mandrel so that the flange fonnsthe helical rib.

The helical tins or ribs, such as rib 21, which are utilized in carryingout the teachings of the present invention may be installed only inthose portions of the pipeline which are inclined to the horizontal atan angle greater than some predetermined angle, 0, at which slumping ofthe solid phase of the slurry material carried by pipeline 11 occurs.This angle would, of course, depend upon such factors as viscosity ofthe liquid. relative densities of the solid andliquid phases of theslurry,

etc. By restricting the location of the ribs in this manner, the.

interference with slurry flow during pipeline transport would beminimizedl In the event the pipeline flow is stopped for any reason,such as repair work, inspection, etc. the solid phase of the slurrymaterial, normally being of greater density than the liquid phasethereof, tends to settle out to form a bed on the bottom of pipeline ll.In the event such settling out occurs in the portions of the pipelineinclined to the horizontal at an angle greater than 0, .the solid phasetends to slump or slide downwardly"within the pipeline. If this slumpingaction is not prev'ented,'a plug of solid phase slurry material may beformed in portions of the pipeline which may hamper restart of thepipeline. By installing fins or ribs similar to rib 21 in those portionsof the pipeline inclined at an angle greater than 0, such slumping isprevented or minimized due to the fact that the settled bed of solidphase slurry material contacts the rib as at 31 (FIG. 2), thuspreventing or minimizing further downward movement thereof within thepipeline.

Rib 21 is only representative of the types of ribs or fins which may beemployed to prevent slumping of the slurry material solid phase. In FIG.3, for example, an alternate form of rib 31a is shown positioned withinpipeline l1. Rib 31a rather than extending about the entire innerperipheral surface of pipeline 1!, is restricted to the bottom half ofthe line with the rib curving back and forth as it progressestherealong. This modification reduces resistance to slurry flow in thepipeline as compared to rib 21 since it is restricted to the bottom ofthe line, while at the same time preventing downward slumping of theslurry material solid phase which has settled out in a bed at the bottomof pipeline 11. Once again, rib 31a may be installed only in thoseportions of pipeline 1] where the angle with respect to the horizontalexceeds angle 0.

Alternatively, as shown in FIG. 4, a plurality of separate short finsegments 3lb-3le may be installed only the lower portions of thepipeline 11 such that the fins will all spiral in the same directionrelative to the pipe. This would eliminate eddys which could be formedwith fins of the configuration of FIG. 3. The fins would not becontinuous, but this would not affect their effectiveness and mayprovide the advantage of providing an unobstructed channel in the top ofthe pipeline for restart.

I claim as my invention:

1. A method for preventing downhill slumping of the solid phase of aslurry material transported by pipeline, said slurry material includinga solid phase and a liquid phase, said method comprising the steps of:

installing within the pipeline at preselected locations a rib whichprojects inwardly into the throughbore defined by the pipeline andcurves back and forth along the bottom half of the pipeline;

restricting the location of the rib to those portions of the pipelinewhich are inclined at an angle to the horizontal slightly less than orgreater than the angle at which slumping of the slurry material solidphase will occur;

said rib projecting into the interior of the pipeline a distancesufficient to engage the slurry material and at least partially preventit from slumping within the pipe when the transport of the slurrymaterial within the pipeline is terminated and said material solid phasesettles within said pipeline.

1. A method for preventing downhill slumping of the solid phase of aslurry material transported by pipeline, said slurry material includinga solid phase and a liquid phase, said method comprising the steps of:installing within the pipeline at preselected locations a rib whichprojects inwardly into the throughbore defined by the pipeline andcurves back and forth along the bottom half of the pipeline; restrictingthe location of the rib to those portions of the pipeline which areinclined at an angle to the horizontal slighTly less than or greaterthan the angle at which slumping of the slurry material solid phase willoccur; said rib projecting into the interior of the pipeline a distancesufficient to engage the slurry material and at least partially preventit from slumping within the pipe when the transport of the slurrymaterial within the pipeline is terminated and said material solid phasesettles within said pipeline.